In general, a biochemical sample contains more than two different materials. Therefore, a separation technique of separating specific components from a mixture for analysis or purification of the components is very important in a sample pretreatment process.
In particular, also in a lab-on-a-chip, wherein microchannels, mixers, pumps, valves, etc. are integrated on a single chip for high-throughput analysis of a small quantity of sample, the sample preparation processes such as purification and separation are key processes that should precede the analysis process.
And, cell-based diagnostics which is important in biological or medical assays embraces blood analysis, cell research, microbiological analysis and tissue transplantation. With the recent development of cell research, cell analysis and protein/DNA analysis techniques, studies on unification and integration of such a clinical diagnostic procedure in the form of a microfluidic device are being conducted.
The microfluidic device for clinical diagnosis refers to a single device in which a series of processes of separating and observing cells to be analyzed, lysing the separated cells and analyzing proteins and DNAs extracted from the cells are integrated. The separation of cells to be analyzed from a sample in which two or more different cells are mixed is an essential procedure to acquire accurate clinical information. For this, a method for separating cells based on microfluidics using the intrinsic difference in physical and chemical properties of cells has been proposed.
Dielectrophoretic separation is based on the difference in dielectrophoretic force occurring when cells are exposed to a non-uniform electric field. U.S. Pat. No. 6,641,708 proposes a method for separating leukocytes using a thin-film chamber forming a velocity profile. Also, a method capable of separating rare target cells with high efficiency by specifically labeling cells with marker particles capable of amplifying the dielectrophoretic force has been reported (PNAS 102; 15757, 2005).
However, although the dielectrophoretic separation allows separation of nonpolar particles and cells without a pretreatment process, a cell-friendly solution cannot be used for the separation because electrolysis may occur in an electrolytic solution such as a cell medium. In addition, for a biological sample containing cells, the separated cells cannot be used for cell therapy because the activity of the cells is affected by the applied voltage.
Meanwhile, in passive separation, cells are separated by the energy required for feeding the sample, unlike the dielectrophoretic separation utilizing external electric field, based on the difference in the density and size of the cells. A cell separation chip used in this passive separation method should be able to separate the cells effectively while having a simple structure to allow easy manufacturing.
Accordingly, there is a need of a cell separation chip capable of effectively collecting/separating only cells in a solution by absorbing the solution containing the cells without the need of applying and maintaining additional external voltage and a method for separating cells using the same.